Visitors look at 'El Neandertal Emplumado', a scientificly based impression of the face of a Neanderthal who lived some 50,000 years ago during the exhibition 'Cambio de Imagen' (Change of Image) at the Museum of Human Evolution in Burgos, Spain. Neandert

Fossilized Neanderthal feces shows man’s ancestors spent at least some time digesting plants, according to a new study that gives the most direct evidence yet of a varied diet.

Carnivorous, or exclusively meat, diets have been the leading theory about what Neanderthals ate, with some scientists suggesting the dominance of meat contributed to their extinction. While meat was their main source of food, they also ate plants, an analysis of fossilized fecal matter showed in a study released today by PLoS One, a publication of the Public Library of Science.

The study found evidence of metabolized plant products in fossilized feces from a 50,000-year-old site in El Salt, Spain. It confirmed research from 2010 that found evidence of plant matter on the teeth of the ancient species and broadens the understanding of Neanderthal behavior and early man, Ainara Sistiaga, the lead author, said in a telephone interview.

“This is the first time that this kind of approach is used in palaeo-biology research,” said Sistiaga, a graduate student at the University of La Laguna in Spain who conducted the analysis while visiting the Massachusetts Institute of Technology in Cambridge. “We are opening a new window into the organic matter in the soil.”

Neanderthals, an ancient species closely related to modern humans, lived in Europe and southwestern and central Asia from about 200,000 to 28,000 years ago. For a time, they coexisted with Homo sapiens but eventually died out.

Digestive tract

The study released today is the first to tie plants into the Neanderthal digestive tract. The samples had high concentrations of broken-down cholesterol also found in the feces of modern humans, showing Neanderthals still ate more meat than greens.

“Our results are the first direct evidence that plants were ingested as part of the diet,” Sistiaga said, though she said plants may have gotten into the digestive tract from eating animal stomachs. It also doesn’t mean the Neanderthals ate anything like a balanced diet, because of the predominance of cholesterol traces.

Isotopes found in bones of Neanderthals have previously suggested a meat-dominated diet, said Alison Brooks, a professor of anthropology at George Washington University in Washington. Fossilized fragments of plant material were found on the teeth of Neanderthals in 2010 as part of research Brooks conducted with other scientists. Those remains may have been from Neanderthals chowing down on stomachs from animals they hunted, other studies have suggested.

The analysis opens a new way to study the biology of early humans, Sistiaga said. The samples at the Spanish site are the oldest fecal matter the method has been used on.

“It confirms what we were arguing about Neanderthal diets and it offers a whole new way of looking at Neanderthal diets,” Brooks, who wasn’t involved in the PLoS One study, said in a telephone interview.